I got some springs for my vortec heads today . Springs are suppose to allow up to .550 lift without machining the heads. Kit consisted of springs, retainers and locks , and cost under $120 with shipping and exchange . I purchased them off e-bay so time will tell how well they work .

Sounds like the Z28 valve spring kit from SDPC2000.com a friend of mine is running them with good results in his GTA